In many processes that employ water, it is desirable that the content of dissolved air or oxygen in the water be lower than the content found in the water as it comes in from a municipal feed line, or as it is recovered in a recycle stream from another processing stage. This is especially the case in processes that employ water in the manufacture of beverages. The dissolved air or oxygen contributes to undesired foaming, undesirable degradation of flavor, and interference with the dissolution of carbon dioxide into the water during the manufacture of carbonated beverages.
The removal of dissolved oxygen is also important in many other industrial processes, such as preparation of syrups and edible oils.
The removal of dissolved gas such as air or oxygen from the water or other liquid is referred to herein as “deaeration”.
Deaeration in the soft drink and brewing industries typically uses carbon dioxide (CO2) as a stripping gas. This has the advantage that any carbon dioxide that absorbs into the water is simply incorporated into the carbonated product. In order to accomplish the desired stripping, the deaerator needs to be run at low pressure (vacuum or atmosphere). At these conditions, equilibrium favors gas removal, but achieving desired gas absorption under these conditions is difficult. This usually means that little carbon dioxide is absorbed into the water, so carbon dioxide losses are high, typically 1 volume of gas (STP) per volume of water.
Current deaeration systems use large amounts of gas, heat, vacuum, or a combination thereof to remove air from the water. Typically, current units simply waste high amounts of carbon dioxide to accomplish the deaeration, or use vacuum pumps and run the deaerator at low pressure. The former is expensive in terms of raw materials (such as carbon dioxide), and the latter is expensive in terms of energy, maintenance, and equipment.
Thus, there remains a need for a method of achieving deaeration of water, which is more effective than current methods and is more efficient in terms of the deaeration achieved per resources (such as carbon dioxide and equipment volumes) expended.